This invention relates to an ink cartridge which is loaded into an ink jet printer for printing, a mounting device for retaining the ink cartridge, and detection plates capable of detecting the amount of ink remaining in the ink cartridge, and when this ink has been depleted.
By way of example, an ink detector is shown in Japanese Patent Laid-Open No. Hei 3-277558 (known example 1), and depicts conventional means for detecting when the amount of ink in an ink cartridge is reduced below a predetermined level by printing. The ink end detector depicted in known example 1 is formed with a pair of electrodes placed in through holes formed on an inner wall face of an ink tank, which is used for supplying ink to a printer head. The depletion of the ink from the ink tank is determined as a change in the conduction state between the electrodes caused by the lack of ink therebetween, and therefore an increased resistance. Seal members for preventing ink leakage from around the electrodes are inserted in the outer periphery of the electrodes positioned within an ink cartridge.
By way of an additional example, an ink cartridge is disclosed in Japanese Patent Laid-Open No. Hei 5-270001 (known example 2). A first of two electrodes for detecting when the amount of ink remaining in the ink cartridge falls below a predetermined level is disposed in a chamber of the ink cartridge. The second of the two electrodes is disposed in an ink outlet port of the ink cartridge. A porous material is placed in the ink outlet port below the second ink outlet electrode for preventing air from being sucked into the ink cartridge when the ink cartridge is removed from a printer by providing a sufficient capillary force, thereby blocking any flow of bubbles into the ink cartridge.
By way of a further example, an ink end detector is disclosed in Japanese Patent Laid-Open No. Hei 6-262772 (known example 3). In this ink end detector one electrode is placed in an opening of the ink cartridge and the other electrode is placed in the cartridge. As the resistance value between the electrodes changes, the sucking and removing of bubbles in the proximity of an ink supply port is performed.
By way of yet another example, an additional known ink end detector is disclosed in Japanese Patent Laid-Open No. Hei 2-198866 (known example 4). In this ink end detector, a mesh electrode is placed so as to cover a portion ink supply port extending into the ink tank from where ink exits the ink cartridge. The mesh electrode covers the inner portion of the ink supply port maintained within the ink tank.
The use of the detectors depicted in known examples 1-3, does not greatly affect the supplying of ink from the ink cartridge to printer means. However, in known examples 1 and 2, since one electrode is placed in the ink supply port, there is some degradation of the detection accuracy of the depletion of ink from the ink tank. Since the distance between the two electrodes is great, the resistance between the electrodes is also great, and as a result, the detection accuracy decreases, and may be affected by environmental changes. The placement of the two electrodes in the ink cartridge, rather than in the ink supply port, reduces this problem. Additionally, as is shown in known example 2, in the ink cartridge with the porous material placed in the ink supply port below the electrode contained therein, foreign material may accumulate on the porous material during use, thereby affecting the detection accuracy. Additionally, the apparatus known example 3 is very complicated and costly.
Additionally, as is depicted in known examples 1 and 2, since one electrode is disposed in an ink reservoir or ink support port, apart from the other electrode in the ink reservoir, porous material positioned between the two electrodes increases the detection resistance value. Thus, the accuracy of detection of the required predetermined change in the resistance value in accordance with ink consumption is reduced. Additionally, it is feared that the detection accuracy may largely vary based on environmental factors, such as temperature. Further, since one of the electrodes is positioned within the ink supply port, the port must be large. However, a cartridge provided with a large number of ink chambers for holding different colors for color printing has limited space. Thus, it becomes difficult to provide adequately large ink supply ports to place the electrode therein.
In known example 4 in which the mesh electrode is disposed so as to cover the inner portion of the ink supply port, the device may inaccurately detect the depletion of ink from the ink tank.
Additionally, in known examples 1 and 2, ink leakage prevention means, comprising a rubber stopper or other seal material, is required to seal the electrode which is disposed in the ink reservoir or ink supply port where the electrode passes through the wall of the ink tank.
In each known example in which one electrode is disposed projecting into the ink reservoir or ink supply port, when ink flows past this electrode, the ink flow is disrupted and bubbles are prone to occur in ink, resulting in unstable and inaccurate detection of the depletion of ink from the ink tank. Therefore, it would be beneficial to provide an ink end detector which overcomes these shortcomings of these known detectors.